The invention relates to a casting mould for the manufacturing of a cooling element for a pyrometallurgical reactor, wherein the casting mould is at least partly cooled and lined with a material that can withstand high temperatures. The invention also relates to the cooling element made in the said mould.
In pyrometallurgical processes, the brickwork of a reactor is protected by water-cooled cooling elements so that, due to the cooling effect, the heat coming to the surface of the brickwork is transferred via the cooling element to water, wherein the wear on the lining decreases considerably in comparison with a reactor not provided with cooling. The decrease in wear is caused by the result of cooling, a so called autogenic lining, formed of slag and other molten phases that attaches to the fireproof surface of the lining.
Traditionally, cooling elements are manufactured by two methods: Firstly, the elements can be fabricated by sand casting. In this method, cooling pipes made of highly thermo-conductive material such as copper are set in a mould dug in the sand, so that during casting, there is cooling either by air or water occurring around the pipes. The element to be cast around the piping is also made of a highly thermo-conductive material, advantageously copper. This fabrication method has been described in for example GB patent 1386645. The problem with this method is the uneven attachment of the piping that acts as flow channel to the surrounding casting material, since part of the piping may be totally detached from the element cast around it and part of the piping may be completely melted and therefore damaged. If no metallic bond is formed between the cooling pipe and the other element cast around it, heat transfer will not be efficient. If the piping melts completely, it will prevent the flow of cooling water. The casting properties of the casting material can be enhanced by, for example, mixing some phosphorus into the copper, which will improve the metallic bond forming between the piping and casting material, but in this way the heat transfer properties (thermal conductivity) of the cast copper deteriorate considerably with just small additions. Advantages of this method can be listed as the comparatively low fabrication costs and independence from dimensions.
A fabrication method has also been used, where glass piping in the shape of a flow channel is set into the cooling element mould which glass piping is broken after casting, so that a flow channel forms inside the element. U.S. Pat. No. 4,382,585 describes another, widely used fabrication method for cooling elements, according to which the element is fabricated for example from rolled copper plate, by machining the necessary channels. The advantage of this method is the dense, strong structure and good heat transfer from a cooling medium such as water to the element. The drawbacks are dimensional limitations (size) and the high cost.
Now a casting mould has been developed for manufacturing a cooling element for a pyrometallurgical reactor to replace the previous sand casting. The casting mould is constructed from separate, highly thermo-conductive copper plates, of which at least some are water-cooled. Since the cooling element itself is in most cases copper, the construction plates of the casting mould should be isolated from the cast copper, and this occurs by lining the inner part of the mould with highly thermo-conductive material such as grapite plate, so that the parts of the mould attach themselves to the surface by means of underpressure. Graphite prevents the melt poured into the mould from sticking to the surface of the mould. The cooling element casting mould is advantageously provided with a cope, so the casting can be done in shielding gas. Prior to casting, the cooling pipes necessary for cooling water circulation that are going to go inside the cooling element are placed into the mould. This piping is preferably made of nickel copper pipe, because the melting point of Nixe2x80x94Cu pipe is higher than the copper being cast around it and therefore there is no risk of the pipe melting during casting.
The essential features of the invention will become apparent in the attached patent claims.
The casting mould construction described in this invention offers the following advantages:
Thanks to the cooled mould and graphite lining, a tight and fine-grained casting is formed, particularly at the base of the casting mould.
The construction of the mould means that the cooling element forms a smooth surface, which is not vulnerable to corroding smelting conditions.
The nickel copper used as the material for the cooling element cooling pipes facilitates a good welding of the piping to the actual element.
The construction of the casting mould can be developed further so that it can also be used for manufacturing cooling elements designed for special purposes. This occurs for example by adding graphite or fireproof shaped pieces to the mould, so that the finished element design differs correspondingly from the plated version.